Fixes a bug where drcachesim -offline complained about an open file across a fork. This bug blocked tracing of SPECCPU perlbench.
Adds a new test of drcachesim -offline with an app that forks. As is, this matched the -satisfy_w_xor_x test regex, and I tried to make it work with that option by fixing a file close bug here. However, I did not have time to figure out another bug which I filed as #5499. I thus tightened the "fork" regex to exclude this test from -satisfy_w_xor_x.
Fixes #5495 (closed)